Building commissioning challenges, solutions: Fire, life safety

Commissioning, recommissioning, or retro-commissioning, can be a challenge—and the more complex a facility is, the more boxes an engineer has to check to get the job done right. Fire and life safety systems have some of the most complex requirements.

Dodd: MNS are now being required on military (government) projects. Water mist systems are being more widely used, providing localized fire protection and water conservation. Intelligibility requirements through the use of digital handheld tools are becoming more commonplace. State-of-the-art technology is impacting life safety systems by making equipment smaller and faster, and increasing communication capabilities.

CSE: What fire/life safety lessons have you learned on past building commissioning projects?

Dodd: The biggest issue is validating interconnection requirements between the fire alarm system, the fire suppression system, and the HVAC systems. A big lesson for us was having a city fire marshal inspect and sign off on the fire/life safety system for a large hospital, and then when we performed some follow-up testing discovering that 50% of the fire/smoke dampers didn’t operate properly.

CSE: What unique requirements do HVAC systems have, and how have they changed in the past 1 to 2 years?

Horkey: As more and more jurisdictions require ASHRAE 90.1-2010, and with the increased popularity of the Architecture 2030 challenge, mechanical systems are maximizing current technology efficiency. These code-mandated requirements as well as the Architecture 2030 requirements make data-based decisions more critical. This increased desire to make decisions based on real-time data increases the need for measurement, verification, instrumentation, and analysis.

Dodd: Chilled beams and variable refrigerant systems (VRS) are two new popular system approaches. A VRS separates conditioning for comfort from ventilation requirements and is easier to implement and operate efficiently. Since the safety factor is lower in order to maximize energy consumption, there can be challenges if loads have been misinterpreted by the architect communicating the needs of the owner, or if the mechanical engineer is not aligned with the assumptions made by the energy modeller. Coordination between modelling, architectural elements, and mechanical design is critical.

CSE: What systems or best practices do you suggest to test the building envelope?

Hendricks: Thermal scans are typically the best approach to identifying envelope issues in large buildings. A compromised building envelope will be the biggest cause of energy loss in most buildings, especially those in colder climates, and thermal scans will immediately identify any areas of heat loss.

Dodd: Testing a leaky envelope only tells you that you have problems that may be very difficult to fix. Best practices are to review the design, review building assemblies depicted in the details, review submittals, and test a mock-up of assembly tie-ins to fend off bigger problems later.

Horkey: Building envelope testing is becoming a very popular component of our commissioning offering. We follow the Building Enclosure Commissioning Process as outlined in ASHRAE Guideline 0-2005 and National Institute of Building Sciences (NIBS) Guideline 3-2012: Building Enclosure Commissioning Process. As a full-service architecture and engineering firm, we have architects who are experts in building envelopes, and they are invaluable for design reviews on new construction. The advancement of infrared camera technology has made the identification of envelope problems much easier in existing buildings.

CSE: What type of test-and-balance or air balancing issues have you resolved?

Dodd: The test-and-balance (TAB) contractor often manually manipulates values and dampers to achieve their overall balance and then forgets to return them to their automatic state. During testing we can see on the BMS graphic that a valve is “closed,” but a physical inspection often reveals that the valve has never changed position. This is a common problem that we bring up in pre-commissioning meetings to try and mitigate.

Hendricks: A major air balancing issue we contend with is stack effect. This is very tricky because most operators will try to combat the phenomenon by modifying the operation of the HVAC system, when in reality the only way to counter stack effect is through compartmentalization. On a new construction project, the commissioning team might be able to influence the design team if potential issues are identified early in the process—yet another reason to make sure the commissioning team is on board right away.

Horkey: Water-side balancing that has consistently been an issue with the popularity of variable frequency drives (VFDs) is using triple-duty valves to set the maximum flow of water pumps. This causes an unnecessary increase in system pressure, which results in increased pumping horsepower. We recommend the triple-duty valve be fully opened and the VFD speed set and adjusted as needed to deliver appropriate flow in the system.